To understand how to truly manage this, we need to understand how estrogen is produced. Excess testosterone/androstendione is converted into estrone/estradial ( or estrogen) by the aromatase enzyme. Various sites in the body convert estrogen: the liver, adrenals, testes (in men) , ovaries (in women)and breasts (in women, and possibly gynecomastia in men). (Other factors that also increase aromatization are excess bodyfat, excess alcohol intake and opiod painkillers, among others.)
When one is on cycle, then their testicular activity is reduced significantly. I believe this is why we hear about guys bottoming out their estrogen when on cycle, even though AI's typically don't lower E that much in men. Conversely, we see men that use HCG (to keep the testes active) have more estrogen management issues. This is likely due to the estrogen conversion that they have in the testes because of their maximized testicular activity. Another factor is that androstendione is still produced, which allows for an additional conversion product to estrogen instead of simply testosterone.
In ye olde tyme days of AAS, guys typically used Proviron on cycle to control estrogen, and if necessary, Nolvadex. However, with the availability, decreased price and superior effectiveness of aromatase inhibitors, this is no longer the preferred method.
Now, you can have gyno without estrogen. Increased aromatization typically causes this to occur. However, once gyno has started, then the increased activity of the ER at breast tissue needs to be addressed. (side note: it's possible that Ostarine and other SARMs can trigger gyno, possibly by activating the ER...)